A simplified model for the prediction of the steady-state outflowthrough a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a ... [more ▼]

A simplified model for the prediction of the steady-state outflowthrough a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a macroscopic control volume. A proper definition of the shape of the control volume enables to take the main characteristics of the flow into account and thus to compensate for the extreme simplification of the spatial representation of the model. At the breach, a relation derived from the shallow-water equations is used to determine the direction of the flow. Developments have been guided by numerical simulations and results have been compared to experimental data. Both the accuracy and the domain of validity of the simplified model are found satisfactory. [less ▲]

A simplified model for the prediction of the steady-state outflow through a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a ... [more ▼]

A simplified model for the prediction of the steady-state outflow through a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a macroscopic control volume. A proper definition of the shape of the control volume enables to take into account the main characteristics of the flow and thus to compensate for the extreme simplification of the space discretisation of the model. At the breach, a relation derived from the shallow-water equations is used to determine the directions of the flow. Developments have been guided by numerical simulations and results have been compared to experimental data. Both the precision and the application domain of the simplified model are found satisfactory. [less ▲]

In a hybrid approach experimental model data are combined with results from 3D and 2D numerical modelling. The latter was conducted by two different models solving the depth-averaged shallow water ... [more ▼]

In a hybrid approach experimental model data are combined with results from 3D and 2D numerical modelling. The latter was conducted by two different models solving the depth-averaged shallow water equations. 3D computations are based on the REYNOLDS-averaged NAVIER-STOKES equations (RANS) using a volume of fluid approach to capture the free water surface. Measurements were performed on a scale model which was especially designed to reproduce the specific conditions of dike breaks. In various simulations it turned out that 2D shallow water models are able to reproduce steadystate flow patterns of dike-break induced flows and that there is a low sensitivity of the solution concerning turbulence modelling, bed and wall roughness. Nevertheless, final flow splits and breach discharges are systematically underestimated. This discrepancy seems to result from inherent modelling assumptions such as zero-vertical velocity and hydrostatic pressure distribution. Therefore, the complementary use of 3D RANS and 2D depth-averaged modelling frameworks for detailed predictions of dike-break induced flows is discussed in the present paper, based on BOUSSINESQ and pressure coefficients, which represent effects of non-uniform velocity profiles and non-hydrostatic pressure distribution over water depth, respectively. Values of these coefficients are inferred from 3D numerical results for the final steady state. [less ▲]

Experimental model data are compared with numerical computations of dike-break induced flows, focusing on the final steady state. An idealised scale model was designed reproducing the specific boundary ... [more ▼]

Experimental model data are compared with numerical computations of dike-break induced flows, focusing on the final steady state. An idealised scale model was designed reproducing the specific boundary conditions of dike breaks. Discharges, water levels and depth profiles of horizontal velocities were recorded and validated by numerical modeling. The latter was performed by two different models solving the two-dimensional depth-averaged shallow water equations, namely a total variation diminishing Runge-Kutta dis¬continuous Galerkin finite element method, and a finite volume scheme involving a flux vector splitting ap¬proach. The results confirmed convergence and general applicability of both methods for dike-break prob¬lems. As regards their accuracy, the basic flow pattern was satisfactorily reproduced yet with differences compared to the measurements. Hence, additional simulations by a finite volume model were performed con¬sidering various turbulence closures, wall-roughnesses as well as non-uniform Boussinesq coefficients. [less ▲]